Showing posts with label Reinforced Cement Concrete. Show all posts
Showing posts with label Reinforced Cement Concrete. Show all posts

Saturday, 25 February 2017

Quality control of Ready Mix Concrete plant.


Introduction

As per Indian Standard code of practice (IS 4926) Ready Mixed Concrete (RMC) is defined as the concrete delivered in plastic condition and requiring no further treatment before being placed in position in which it is to set and harden. Instead of being batched and mixed on site, concrete is delivered for placing from central batching plant. First RMC was patented in Germany in 1903, but the transportation system it had not done properly introduced to achieve proper workability of concrete. The first delivery of RMC was made in Baltimore in 1913, and the transit mixer was born in 1926. In 1931 erected a plant at Bedfont, west of London and launched a company named as Ready Mixed Concrete Ltd.

What is need of RMC plant?

The consumer wanted his concrete delivered to the job in a ready-to-place condition. Volume batching is completely replaced by the weight batching and presently computerized weigh batchers are used in most of the batching plants. Aggregates are stored in properly installed bins and cement and flyash are stored in silos. Conveyors are used to transport the aggregates. Cement and flyash is pumped into the central mixer with pneumatic pumps. Electronic moisture meters, digital admixture dispensers are used in fully automatic batching plants. So due to such practices in RMC plant the workable concrete can produce which may be more durable, because of that there is a need of RMC plant.

Friday, 17 June 2016

Slope deflection method sway portal frame numerical probleam

Analysis the portal frame shown in following fig. by Slope deflection method and draw bending moment diagram.


Answer:-

Slope deflection method is help to determine the bending moment of sway portal frame.

Step 1:-  At fixed support the angle is zero i,e it and the deflection in beam as a delta is shown in fig. All loads are applied on it.





Step 2:- Very 1st the calculation of fixed end moment is determine by using simple fixed end formulas. And the sign convension are placed -ve & +ve respectively.

Wednesday, 15 June 2016

PLASTERING


Applying mortar on the surfaces of walls, columns, ceiling etc. to get smooth finish is termed as plastering.

Mortar used for plastering may be lime mortar, cement mortar or lime-cement mortar.

Lime mortar used lime to sand ratio of 1 : 3 or 1 : 4.

Cement mortar of 1 : 4 or 1 : 6 mix is very commonly used for plastering, richer mix being used for outer walls.

Compaction factor test.


This is another test to  identify the workability of concrete. This test is conducted in the laboratory.

The test equipment consists of two hoppers and a cylinder fixed to a stand, the dimensions and the distances between the three vessels being standardized. Vessel A and B are having hinged bottoms whereas cylinder C is having fixed bottom.

What is CEMENT & its Chemical properties


Cement is a commonly used binding material in the construction. The cement is obtained by burning a mixture of calcarious and argillaceous material at a very high temperature and then grinding the clinker so produced to a fine powder.

It was first produced by a mason Joseph  Aspdin in England in 1924. He named it as portland cement.

#Chemical properties of ordinary portland cement.

What is stone ?


Stone is a ‘naturally available building material’ which has been used from the early age of civilization. It is available in the form of rocks, which is cut to required size and shape and used as building block. It has been used to construct small residential buildings to large palaces and temples all over the world.

A. Type of Stones

• Geological   • Physical    • Chemical

Monday, 6 June 2016

What is membrane curing?


Sometimes, concrete works are carried out in places where there is acute shorting of water. the lavish application of water for water curing is not possible for reason of economy.

It has been pointed out earlier that curing does not mean only application of water, it means also creation of condition for promotion of uninterrupted and progressive hydration.

Membrane curing is a good method of maintaining a satisfactory state of wetness in the body of concrete to promote satisfactory state of wetness in the body of concrete to promote condition hydration when original water/cement ratio used is not less that 0.5. to achieve best result, membrane is applied after one or two days of actual wet curing.

Since no replenishing of water is done after the membrane has been applied it should be ensure that the membrane is of good quality and it is applied effectively. two or three coats may be requires for effective sealing of the surface to prevent the evaporation of the water.

when water proofing paper or polyethylene paper are used care must be taken to see that these are not punctured anywhere and also whether adequate lapping is given at the junction and this is effectively sealed.

Water curing


This is by far the best method of curing as it satisfies all the requirements of curing, namely, promotion of hydration, elimination of shrinkage and absorption of the heat of hydration. it is desirable that a certain extent of water curing is done before the concrete is covered with membranes. water curing can be done in following ways:-

1. Immersion

2. Ponding

3. Spraying

4. Wet covering

the precast concrete items are normally immersed in curing tanks for a certain duration. pavement slabs, roof slabs etc. are covered under water by making small  ponds. vertical retaining wall or plastered surfaces or concrete column etc. are cured by spraying water. In some cases, wet covering such as wet gunny bags, hessian cloth, jute matting, straw etc. are wrapped to vertical surface for keeping the concrete wet. for horizontal surfaces saw dust, earth or sand are used as wet covering to keep the concrete in wet condition for longer time so that the concrete is not unduly dried to prevent hydration.

Slump Test


Slump test is the most commonly used method of measuring workability of concrete. the apparatus for conducting the slump test essentially consists of a metallic mould in the form of a frustum of a cone having the internal dimensions as follows:-

Bottom diameter   20cms

Top diameter          10cms

Height                      30cms

The mould is the place on a smooth, horizontal, rigid and non absorbent surface. the mould is then filled in four layer each approximately 1\4 of the mould. each layer is tamped 25 times by the tamping rod taking care to distribute the stroke evenly over the cross sections. After the top layer has been rodded, top is struck off level with a trowel and tamping rod. the mould is removed from the concrete immediately by raising it slowly and carefully in a vertical direction. this allows the concrete to subsidence. this subsidence is referred as slump of concrete. the difference in level between the height of the mould and that of the height point of the subsided concrete is measured. this difference in height in mm is taken as slump of concrete.

slump requirement for beams and slabs 50mm to 100mm

for walls and columns 75mm to 100mm

Vibrated concrete 15mm to 25mm  

what are the partial properties of workability ?


Mixability, Transportability, Mouldability and Compactibility are the partial properties of workability.

a)  Mixability:-

It is the ability of the mix to produce a homogeneous green concrete from the constituent materials of the batch, under the action of the mixing forces

b) Transportability:-

Transportability is the capacity of the concrete mix to keep the homogeneous concrete mix to keep the homogeneous concrete mix from segregating during a limited time period of transportation of concrete.

c) Mouldability:-

It is the ability of the fresh concrete mix to fill completely the forms or moulds without losing continuity or homogeneity under the available techniques of placing the concrete at a site.

d) Compactibility:-

Compactibility is the ability of concrete mix to be compacted into a dense, compact concrete, with minimum voids, under the existing means of compaction at the site.

What is Workability of concrete ?


The ease with which the concrete can be mixed up with minimum quantity of water, transported, placed and compacted without segregation and bleeding is called workability.

Workability is defined as the property of concrete which determines the amount of useful internal work necessary to produce full compaction. workability concrete is one which exhibits very little internal friction between particle and particle.

The factor helping concrete to have more lubricating effect to reduce internal friction are as follows:-

a. water content

b. mix proportion

c. size of aggregate

d. surface texture

d. shape of aggregate

f. grading of aggregate

g. use of admixture.

Tuesday, 2 February 2016

Moment Distribution Method Portal Frame Numerical

In this video i completely explained the procedure for solving the MDM of portal frame. This method is very important for analysis of any building. We can solve this method by fallowing steps:-

1_ Determination of Fixed End Moments
2_ Determination of stiffness factor
3_ Determination of Distribution factor
4_ Solving sway and non sway MDM table to get joints moments
5_ Determination of sway correction factor
6_Simple bending moments
7_Final bending moments diagram

                                      Watch the video to learn Moment Distribution Method


Saturday, 2 January 2016

Grade of concrete

Characteristic strength is defined us the strength of material below which not more than 5% of test results are expected to full. 

The concrete grade M10, M15 and M20 are termed as ordinary concrete and those of M25 to M55 are termed as standard concrete and the concrete of grade 60 and above are termed as high strength concrete. 

 The selection of minimum grade of concrete is dictated by durability considerations which are based on kind of environment to which the structure is exposed, though the minimum grade of concrete for reinforced concrete is specified as M20 under mild exposure conditions, it is advisable to adopt a higher grade.  

 For moderate, severe, very severe and extreme exposure conditions, M25, M30, M35 & M40 grades respectively are recommended.